Suppression of banding and transient signal oscillations in balanced SSFP using a spoiled RF pre-phasing approach

The ideal excitation pattern produced by the B1a sub-pulse has uniform intensity and an in-plane phase variation θ(x,y) = –πΔf(x,y) TR. To produce such a pattern it is necessary to use either multiple transmit coils as proposed in [1], a 3D RF pulse as done here, or a combination of the two. In this work a slice-selective tip-down pulse (B1a) with 2D in-plane phase variation was designed using a small-tip method with an echo-volumar excitation k-space trajectory and a measured B0 map, with (kx,ky) phase-encoding locations selected using a sparse approximation approach [3]. The tip-up pulse (B1b) was created by first designing an intermediate tip-down pulse B1b,int using the negative of the measured B0 map. The tip-up pulse was then obtained as the negative, time-reverse of B1b,int (with the x and y gradients also negated). The proposed 3D RF pulse design approach is fully compatible with parallel excitation, and as such offers a general approach for creating the desired subpulses given the available RF transmission hardware.